diff --git a/transform/interface-lowering.go b/transform/interface-lowering.go
index d64f2731..6aa3bb13 100644
--- a/transform/interface-lowering.go
+++ b/transform/interface-lowering.go
@@ -616,10 +616,19 @@ func (p *lowerInterfacesPass) createInterfaceMethodFunc(itf *interfaceInfo, sign
 	// Create entry block.
 	entry := p.ctx.AddBasicBlock(fn, "entry")
 
-	// Create default block and make it unreachable (which it is, because all
-	// possible types are checked).
+	// Create default block and call runtime.nilPanic.
+	// The only other possible value remaining is nil for nil interfaces. We
+	// could panic with a different message here such as "nil interface" but
+	// that would increase code size and "nil panic" is close enough. Most
+	// importantly, it avoids undefined behavior when accidentally calling a
+	// method on a nil interface.
 	defaultBlock := p.ctx.AddBasicBlock(fn, "default")
 	p.builder.SetInsertPointAtEnd(defaultBlock)
+	nilPanic := p.mod.NamedFunction("runtime.nilPanic")
+	p.builder.CreateCall(nilPanic, []llvm.Value{
+		llvm.Undef(llvm.PointerType(p.ctx.Int8Type(), 0)),
+		llvm.Undef(llvm.PointerType(p.ctx.Int8Type(), 0)),
+	}, "")
 	p.builder.CreateUnreachable()
 
 	// Create type switch in entry block.
diff --git a/transform/testdata/interface.ll b/transform/testdata/interface.ll
index ee059c95..1e2ce61b 100644
--- a/transform/testdata/interface.ll
+++ b/transform/testdata/interface.ll
@@ -24,6 +24,7 @@ declare void @runtime.printuint8(i8)
 declare void @runtime.printint32(i32)
 declare void @runtime.printptr(i32)
 declare void @runtime.printnl()
+declare void @runtime.nilPanic(i8*, i8*)
 
 define void @printInterfaces() {
   call void @printInterface(i32 ptrtoint (%runtime.typeInInterface* @"typeInInterface:reflect/types.type:basic:int" to i32), i8* inttoptr (i32 5 to i8*))
diff --git a/transform/testdata/interface.out.ll b/transform/testdata/interface.out.ll
index 80f71ee4..4bb9ec1b 100644
--- a/transform/testdata/interface.out.ll
+++ b/transform/testdata/interface.out.ll
@@ -25,6 +25,8 @@ declare void @runtime.printptr(i32)
 
 declare void @runtime.printnl()
 
+declare void @runtime.nilPanic(i8*, i8*)
+
 define void @printInterfaces() {
   call void @printInterface(i32 4, i8* inttoptr (i32 5 to i8*))
   call void @printInterface(i32 16, i8* inttoptr (i8 120 to i8*))
@@ -83,6 +85,7 @@ entry:
   ]
 
 default:                                          ; preds = %entry
+  call void @runtime.nilPanic(i8* undef, i8* undef)
   unreachable
 
 "reflect/types.type:named:Number":                ; preds = %entry